Method and system for temporal synchronization

ABSTRACT

Embodiments of the present invention provide a method, apparatus and system for temporal synchronization of digital content based on a marker symbol and a marker code. A marker symbol is inserted at an identifiable location of a payload (e.g., the beginning and/or end of a payload) at regular intervals in the digital content and the payload is marker coded to form a periodic sequence. The payload is marker coded such that the maker symbol is not repeated by the coded payload. The periodic sequence is then embedded into digital content. A decoder is able to re-synchronize the payload by determining the location of the marker symbol. As such, a method, apparatus and system is provided for robust temporal synchronization for, for example, content encoding and decoding for applications such as audio and video water-marking and the like.

This application claims the benefit, under 35 U.S.C. §365 ofInternational Application PCT/US2006/046815 filed Dec. 8, 2006, whichwas published in accordance with PCT Article 21(2) on Jan. 24, 2008 inEnglish and which claims the benefit of United States provisional patentapplication Serial No. 60/831,526 filed Jul. 18, 2006.

FIELD OF THE INVENTION

The present invention generally relates to digital content security and,more particularly, to a method and system for temporal synchronizationfor encoding and decoding digital content.

BACKGROUND OF THE INVENTION

For the encoding and decoding of digital content, synchronization playsa vital role. For example, in a digital watermarking environment,synchronization (also called registration) is vital for payload decodingin applications such as watermarking. For audio and video watermarking,the synchronization typically takes the form of a temporalsynchronization, though some video watermarking methods also requirespatial synchronization. Common methods for watermark synchronizationcan be classified into four major categories:

-   [1] Geometrically invariant transform based, where the watermark is    embedded in a signal transform domain that is invariant to specific    geometric transformations.-   [2] Recovery assisted methods, where a synchronization signal or an    autocorrelation of a periodic watermark will be utilized for    synchronization.-   [3] Feature based, where the watermark is embedded into semantically    meaningful features of the content.-   [4] Exhaustive search, where the detection is running over all    possible geometric distortions.

However, current synchronization schemes have noted deficiencies. Forexample, assume a payload, p, is an N-bits binary sequence b_0 b_1 b_2 .. . b_{N−1}, where b_i=0 or 1, for 0<=i<N. Further assume that thepayload, p, will be repeatedly embedded into the content as b_0 b_1 b_2. . . b_{N−1} b_0 b_1 b_2 . . . b_{N−1} . . . b_0 b_1 b_2 . . . b_{N−1}.During decoding, due to cropping, insertions, deletions and/orsubstitutions (collectively, IDS), etc., some payload bits might belost, some might be incorrectly decoded, and some additional bits mightbe added. Thus the decoded sequence may look like b_3 b_4 b_6 b_7 b_8a_0 b_9 a_1 b_11 b_12 . . . , where in this example, b_0, b_1, b_2 arecropped, b_5 is deleted, an additional bit a_0 is inserted between b_8and b_9, b_10 is substituted by a_1.

As such, what is needed is a robust synchronization scheme for digitalcontent that overcomes IDS degradations.

SUMMARY OF THE INVENTION

The present invention addresses the deficiencies of the prior art byadvantageously providing a method, apparatus and system for temporalsynchronization of received digital content, such as audio and videowatermarked content, to enable robust encoding and decoding of thedigital content.

In one embodiment of the present invention, a method for temporalsynchronization of digital content includes determining at least onemarker symbol and a corresponding marker code such that when the digitalcontent is coded using the marker code, the marker symbol is notrepeated by the coded digital content, embedding the determined markersymbol in an identifiable location in a payload of the digital contentand coding the payload of the digital content using the determinedmarker code to form a periodic sequence. The coded digital content canbe temporally synchronized for decoding by identifying the marker symbolin the payload of the digital content, the marker symbol marking anidentifiable location in the payload for use in decoding the payload ofthe digital content.

In an alternate embodiment of the present invention, a method fortemporal synchronization of digital content includes receiving digitalcontent having an embedded, unique marker symbol in a payload of thedigital content, the digital content having been coded via a marker codeto form a periodic sequence, temporally synchronizing the digitalcontent for decoding by identifying the marker symbol in the payload ofthe digital content, the marker symbol marking an identifiable locationin the payload for use in decoding the payload of the digital content,and decoding the payload of the digital content using at least alocation of the identified marker symbol and the marker code.

In an alternate embodiment of the present invention, an apparatus fortemporal synchronization of digital content for use in encoding thedigital content includes a marker generation/coding unit configured todetermine at least one marker symbol and a corresponding marker codesuch that when the digital content is coded using the marker code, themarker symbol is not repeated by the coded digital content, to embed thedetermined marker symbol in an identifiable location in a payload of thedigital content, and to code the payload of the digital content usingthe determined marker code to form a periodic sequence.

In an alternate embodiment of the present invention, an apparatus fortemporal synchronization of digital content for use in encoding thedigital content includes a marker decoding unit configured to receivedigital content having an embedded, unique marker symbol in a payload ofthe digital content, the digital content having been coded via a markercode to form a periodic sequence, to temporally synchronize the digitalcontent for decoding by identifying the marker symbol in the payload ofthe digital content, the marker symbol marking an identifiable locationin the payload for use in decoding the payload of the digital content,and to decoding the payload of the digital content using at least alocation of the identified marker symbol and the marker code.

In an alternate embodiment of the present invention a system fortemporal synchronization of digital content includes a markergeneration/coding unit and a marker decoding unit. The markergeneration/coding unit is configured to determine at least one markersymbol and a corresponding marker code such that when the digitalcontent is coded using the marker code, the marker symbol is notrepeated by the coded digital content, to embed the determined markersymbol in an identifiable location in a payload of the digital content,and to code the payload of the digital content using the determinedmarker code to form a periodic sequence. The marker decoding unit isconfigure to receive digital content having an embedded, unique markersymbol in a payload of the digital content, the digital content havingbeen coded via a marker code to form a periodic sequence, to temporallysynchronize the digital content for decoding by identifying the markersymbol in the payload of the digital content, the marker symbol markingan identifiable location in the payload for use in decoding the payloadof the digital content, and to decoding the payload of the digitalcontent using at least a location of the identified marker symbol andthe marker code.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 depicts a high level block diagram of a system for encoding anddecoding received content including temporal synchronization inaccordance with an embodiment of the present invention;

FIG. 2 depicts a high level block diagram of an embodiment of a markerunit suitable for use as a marker generation/encoding unit and/or amarker decoding unit in the encoding and decoding system of FIG. 1;

FIG. 3 depicts a high level block diagram of a method of an encoder inaccordance with an embodiment of the present invention; and

FIG. 4 depicts a high level block diagram of a method of a decoder inaccordance with an embodiment of the present invention.

It should be understood that the drawings are for purposes ofillustrating the concepts of the invention and are not necessarily theonly possible configuration for illustrating the invention. Tofacilitate understanding, identical reference numerals have been used,where possible, to designate identical elements that are common to thefigures.

DETAILED DESCRIPTION OF THE INVENTION

The present invention advantageously provides a method, apparatus andsystem for temporal synchronization of received digital content, such asaudio and video watermarked content, to enable robust encoding anddecoding. Although the present invention will be described primarilywithin the context of a stand alone recovery assisted method having anembedded marker symbol and marker code on the payload of watermarkedcontent and being marker coded and decoded by a respective, encoder anddecoder, the specific embodiments of the present invention should not betreated as limiting the scope of the invention. It will be appreciatedby those skilled in the art and informed by the teachings of the presentinvention that the concepts of the present invention can beadvantageously applied using other special structures transmitted withor embedded in the payload and can be marker coded and decoded in standalone devices. In addition the concepts of the present invention can bejointly used with other synchronization methods, such as the embeddingof a synchronization signal or the combination with a feature basedwatermarking method.

The functions of the various elements shown in the figures can beprovided through the use of dedicated hardware as well as hardwarecapable of executing software in association with appropriate software.When provided by a processor, the functions can be provided by a singlededicated processor, by a single shared processor, or by a plurality ofindividual processors, some of which can be shared. Moreover, explicituse of the term “processor” or “controller” should not be construed torefer exclusively to hardware capable of executing software, and canimplicitly include, without limitation, digital signal processor (“DSP”)hardware, read-only memory (“ROM”) for storing software, random accessmemory (“RAM”), and non-volatile storage. Moreover, all statementsherein reciting principles, aspects, and embodiments of the invention,as well as specific examples thereof, are intended to encompass bothstructural and functional equivalents thereof. Additionally, it isintended that such equivalents include both currently known equivalentsas well as equivalents developed in the future (i.e., any elementsdeveloped that perform the same function, regardless of structure).

Thus, for example, it will be appreciated by those skilled in the artthat the block diagrams presented herein represent conceptual views ofillustrative system components and/or circuitry embodying the principlesof the invention. Similarly, it will be appreciated that any flowcharts, flow diagrams, state transition diagrams, pseudocode, and thelike represent various processes which may be substantially representedin computer readable media and so executed by a computer or processor,whether or hot such computer or processor is explicitly shown.

In temporal synchronization, two important issues arise. A firstinvolves the identification of a specific location in the digitalcontent (e.g., the beginning and/or the end of a watermark sequence). Asecond issue involves how robust the marking and location identificationis against insertions, deletions, and substitutions (IDS). As a digitalcontent (such as a video frame or a block of audio samples) is subjectto data insertion, deletion, and/or substitution, robustness against IDSis crucial for payload decoding.

A temporal synchronization method, apparatus and system is described inaccordance with various embodiments of the present invention. Thedescribed method, apparatus and system include a special structureimposed on the payload in accordance with an embodiment of the presentinvention. For example, in one embodiment of the present invention, amarker code represents the payload such that automaticre-synchronization in a decoding process can be accomplished. Themethods of the embodiments of the present invention can be jointly usedwith other synchronization methods, such as an embedded synchronizationsignal or combination with a feature based watermarking method.

FIG. 1 depicts a high level block diagram of a system for encoding anddecoding received digital content including temporal synchronization inaccordance with an embodiment of the present invention. The system 100of FIG. 1 illustratively comprises a digital content source 105 (e.g., adigital camera), an encoder 110, a decoder 115 and an output device 120.The encoder 110 of FIG. 1 comprises a marker generation/coding unit 112and a transmitting device (e.g., a transmitting antenna) 114. Thedecoder 115 of FIG. 1 comprises a marker decoding unit 117 and areceiving device (e.g., a receiving antenna) 119.

In the system 100 of FIG. 1, the encoder 110 receives the digitalcontent from the digital content source 105. In accordance with anembodiment of the present invention, marker generation/coding unit 112determines a unique marker symbol and inserts the marker symbol atregular intervals in the received digital content (the payload). At thedecoder 115, by searching for special marker symbols, the decoder willbe able to identify the location of the marker symbol in the payload(i.e., the beginning or the end of one complete interval of the payload)and as such properly decode the content by, for example, aligning themarker symbols. In one embodiment of the present invention, a system ofthe present invention can include watermark embedding. It should benoted however, that even with a watermark embedder inserting markersymbols at regular intervals, the watermark decoder could still havedifficulty identifying one complete payload interval due to IDS.

More specifically, in a non-watermarking data synchronizationapplication, it can be assumed that the data block length is unchangedfrom encoding to decoding. In such a scenario, a marker symbol of thepresent invention would be searched for in the content at knownlocations for use in temporal synchronization of the encoded and to bedecoded content. That is, if two such marker symbols are found within adistance equal to a content interval (e.g., the data block length), thenthe data can be synchronized to align to the two marker symbols.

On the other hand, in a digital watermarking application and the like,some payload bits could be lost and/or some non-payload bits could beadded because of IDS; that is a host signal can be distorted. Thus, itcould not be assumed the data block length is constant any more. Inaddition, it is possible that the marker symbol is identical to aportion of the payload, which adds another ambiguity. As such and inaccordance with embodiments of the present invention, to make a markercoding of the present invention more robust and work for watermarksynchronization and the like, further coding of the payload bits isherein proposed, in additional to the insertion of a special markersymbol. In various embodiments of the present invention, the proposedmarker coding method is applied during payload generation. In contrast,most current synchronization methods are applied after payloadgeneration. For example, geometrically invariant transform based methodsand feature based methods are applied during watermark embedding,exhaustive search methods are applied at the detection stage, andsynchronization or autocorrelation methods are applied after payloadgeneration. It should be noted however, that embodiments of the presentinvention can be combined with other synchronization methods such asthose described above. That is, the embodiments of the methods of thepresent invention work at the inner layer (payload generation) of adigital watermarking system, and provide an additional layer ofrobustness for temporal synchronization.

Referring back to FIG. 1, in one embodiment of the present invention,the marker generation/coding unit 112 in addition to determining aunique marker symbol, also performs marker coding. More specifically inone embodiment of the present invention, a k-bits binary number isselected (for example, it could be all zeros 0 0 . . . 0) as the markersymbol, and is inserted at an identified position in the payload, p(i.e., at the beginning or the end of the payload). Subsequently,selected code words for marker coding are used such that the markersymbol is not repeated, in the payload. Even further, code words can beselected such that specific code words that would result in payload bitssomewhat resembling the marker symbol are not used for marker coding thepayload. For example, in one embodiment of the present invention, mreserved k-bits binary numbers are selected such that the m selectedcode words will not be used for encoding the payload. A reason for usingcode words that will not be used for encoding the payload is to increasethe robustness of temporal synchronization from the marker symbol of thepresent invention.

For example, in one embodiment of the present invention, the number m isranging from 0 to (2^k−3). For a given m, a closed form procedure fordetermining the reserved code words can be derived. For the remaining(2^k−m−1) code words, where each is k-bits long, they are used torepresent the payload, p, for example, to convert p from its binaryrepresentation to a new representation whose base is (2^k−m−1) and whosecode words are k-bits long. For example, for the two extreme cases: whenm=0, there is no reserved code word, every code word except the markersymbol will be used for marker coding; when m=2^k−3, only two code wordsare left for payload representation, thus every bit of the payload willbe represented by a k-bits code word. After the payload representation,error correction encoding can be applied and then repeated embedding canbe applied in the digital content.

To easily identify the marker symbol and to maximize the minimumdistance between code words and marker symbol (i.e., Hamming distance orother distance measure, depending on the decoder being used), a markersymbol can be selected such that any combination of the (2^k−m−1) codewords will be different from the marker symbol, as seen in the followingexample.

The marker code can be illustrated with a simple example. In thisexample, k=3 and 0 0 0 is chosen as the marker symbol. Three code words1 0 0, 0 1 0, and 0 0 1, where each is different from the marker symbol0 0 0 by only one bit, are reserved and not used for encoding thepayload to maximize robustness. As there are four possible code words (01 1, 1 0 1, 1 1 0, and 1 1 1) left, the payload, p, can be representedin a base four (4) representation system using these four code words. Assuch, every two bits in the payload, p, can be mapped into one of thefour code words 0 1 1, 1 0 1, 1 1 0, and 1 1 1.

For example, the following code can be defined as follows:

-   0 0→0 1 1-   0 1→1 0 1-   1 0→1 1 0-   1 1→1 1 1    where the left side depicts 2-bits from the payload, p, and the    right side depicts the corresponding 3-bit code word. With the    marker symbol 0 0 0 at the beginning, the payload after marker    coding will have (3N/2+3) bits. These (3N/2+3) bits will be further    error correction encoded and repeatedly embedded into the digital    content.

A special property of the above marker code example is that there is atmost one “0” in each of the four code words 0 1 1, 1 0 1, 1 1 0, and 11 1. As a consequence, there will be no three consecutive “0” in themarker code of a payload, except the marker symbol 000 at, for example,the beginning of a payload.

The marker coded content having the embedded marker symbol is thencommunicated via the transmitting device 114 to the decoder 115 andreceived by the decoder 115 via the receiving device 119. The markerdecoding unit 117 in the decoder 115 examines the received content forthe marker symbol. That is, if the marker decoding unit 117 identifiesthe marker symbol (e.g., three consecutive “0”) in a marker code of arepeatedly embedded payload, it will immediately determine with highconfidence that it has found an identifiable location (e.g., thebeginning) of a payload. As such, the present invention enables the easyidentification of a specific location of the payload (i.e., thebeginning or end of a payload) and a location for the re-synchronizationof the payload during, for example, decoding.

With respect to decoding, take for example a 16-bits payload 0 1 0 1 0 01 1 0 1 1 0 1 0 1 1. A corresponding marker code in accordance with anembodiment of the present invention can be 0 0 0 1 0 1 1 0 1 0 1 1 1 1 11 0 1 1 1 0 1 1 0 1 1 1, where the first three bits “000” is the markersymbol, the next three bits “101” is the marker code of the bits 1 and 2(“01” of the payload), the next, three bits “101” is the marker code ofthe bits 3 and 4 (“01” of the payload), etc. This 27-bits marker codecan be error correction coded and repeatedly embedded into the digitalcontent at the encoder side. At the decoder side, after, for example,extraction and error correction decoding, the marker decoding unit 117examines the marker code for three consecutive “0”. When threeconsecutive “0” are located, the marker decoding unit 117 determines alocation for temporal synchronization of the payload sequence. Themarker symbol location and the marker code can then be used to decodethe digital content. The decoded digital content can then becommunicated to the output device 120.

It should be noted, however, that because of IDS or other signalprocessing operations on the watermarked, content, instances can occurwhen there are no three consecutive “0” in the decoded sequence. Inaccordance with the present invention, a maximum likelihood principlecan be applied by the marker decoding unit 117, to determine whichpayload sequence is most likely the marker symbol embedded in thecontent. More specifically and referring to the example above, becausein the above described embodiment of the present invention, only fivecode words, “000”, “011”, “101”, “110”, and “111”, are used in theencoder, a maximum likelihood principle can be applied to the markercoded digital content to determine which payload sequence is most likelythe marker symbol embedded in the content.

Although in FIG. 1, the marker generation/coding unit 112 and the markerdecoding unit 117 are depicted as being integrated in the encoder 110and the decoder 115, respectively, in alternate embodiments of thepresent invention, the marker generation/coding unit 112 and the markerdecoding unit 117 of the present invention can be stand-alone units forimplementing the aspects of the present invention. For example, FIG. 2depicts a high level block diagram of an embodiment of a marker unitsuitable for use as a marker generation/encoding unit 112 and/or amarker decoding unit 117 in the encoding and decoding system 100 of FIG.1 in accordance with the present invention. The marker unit of FIG. 2comprises a processor 210 as well as a memory 220 for storing controlprograms, algorithms, marker symbols and marker codes and the like. Theprocessor 210 cooperates with conventional support circuitry 230 such aspower supplies, clock, circuits, cache memory and the like as well ascircuits that assist in executing the software routines stored in thememory 220. As such, it is contemplated that some of the process stepsdiscussed herein as software processes may be implemented withinhardware, for example, as circuitry that cooperates with the processor210 to perform various steps. The marker unit also contains input-outputcircuitry 240 that forms an interface between the various respectivefunctional elements communicating with the marker unit.

Although the marker unit of FIG. 2 is depicted as a general purposecomputer that is programmed to perform various control functions inaccordance with the present invention, the invention can be implementedin hardware, for example, as an application specified integrated circuit(ASIC). As such, the process steps described herein are intended to bebroadly interpreted as being equivalently performed by software;hardware, or a combination thereof.

FIG. 3 depicts a high level block diagram of a method of an encoder inaccordance with an embodiment of the present invention. With referenceto FIG. 3, a watermark payload having 64-bits is assumed. The payload ofFIG. 3 could go through a lossless compression first and encryptionnext, though the compression and/or encryption steps could be omitted insome cases. The method 300 of FIG. 3 begins at step 302 in which digitalcontent (e.g., a 64-bit payload) is received by, for example, a markergeneration/coding unit of an encoder for marker coding in accordancewith the present invention. The method 300 then proceeds to step 304.

At step 304, a 6-bit cyclic redundancy check (CRC) code is appended tothe end of the payload, which increases the payload length to 70-bits.The method 300 then proceeds to step 306.

At step 306, a marker symbol is determined and embedded into the payloadand a corresponding marker code is applied to the payload to derive anew sequence of 3*70/2+3, which results in a payload of 108-bits. Thatis, as described above 0 0 0 can be selected as the marker symbol and inone example inserted into the beginning of the payload, and every twobits of the payload can be coded into one of the code words 0 1 1, 1 01, 1 1 0, and 1 1 1. As described above, in various embodiments of thepresent invention, the marker symbol and marker code are determined suchthat the code words will be different from the marker symbol such thatthe marker symbol will not be repeated in marker encoded content. Themethod 300 then proceeds to step 308.

At step 308, a rate ½ convolutional encoding is applied to the 108-bitssequence to obtain a binary sequence of 216-bits. The method 300 thenproceeds to step 310.

At step 310, the 216-bits sequence is repeatedly embedded into thecontent, for example a video sequence, where each frame represents onebit information of the 216-bit sequence. Various known embeddingtechniques can be applied and as such the invention should not belimited to any specific embedding method. Thus, for a three-minute videosequence with a frame rate of 24 frames per second, the embedding willbe repeated 3*60*24/216, which results in an embedding of 20 times,assuming no additional synchronization signal. The encoding method 300can then be exited or can optionally proceed to step 312.

At step 312, an additional synchronization signal can be optionallyembedded to further enhance the robustness of the synchronization of thepresent invention.

FIG. 4 depicts a high level block diagram of a method 400 of a decoderin accordance with an embodiment of the present invention. The method400 of FIG. 4 begins at step 402 in which content encoded in accordancewith embodiments of the present invention (i.e., the coding of themethod of FIG. 3) is received by, for example a marker decoding unit ofa decoder of the present invention. The method 400 proceeds to step 404.

At step 404, if there is a frame rate change, the method proceeds tostep 406 in which the content is re-sampled. The method then proceeds tostep 408. If there is no frame rate change, the method 400 proceeds tostep 408.

At step 408, 1-bit information is extracted from each frame. The method400 then proceeds to step 410.

At step 410, the extracted binary sequence is decoded. If there is nodistortion from the encoding to the decoding path, the decoded sequencewill be a 20 times repeated 108-bit sequence. However, due to cropping,frame addition or deletion, and/or other signal processing operations ormalicious attacks, the decoded sequence can be different from error-freerepeated 108-bit sequence. After decoding, the method 400 proceeds tostep 412.

At step 412, the decoded content is examined for the marker symbol(e.g., three consecutive zeroes (0 0 0)). If the marker symbol islocated, the method 400 skips to step 416. If the marker symbol is notlocated, the method 400 proceeds to step 414, in which a maximumlikelihood process is performed to determine which payload sequence ismost likely the marker symbol embedded in the content. The method 400then proceeds to step 416.

At step 416, the content undergoes marker decoding. That is, because aknown position in the content is identified by the marker symbol (i.e.,the beginning of the content is identified and as such temporalsynchronization is achieved) the content can undergo marker decodingusing a reverse process of the marker coding described above. The method400 then proceeds to step 418.

At step 418, the marker decoded content is examined to determine if the6-bits after the next 64-bits matches the embedded CRC. If the embeddedCRC is verified then it can be assumed that the payload has beencorrectly decoded and the method is exited. If the CRC does not matchfor all the cases where the marker symbol is found, then, in oneembodiment of the present invention, the method 400 can proceed one stepfurther to step 420.

At step 420, payload bits preceding the marker symbol and payload bitsafter the marker symbol are collected (i.e., the payload sequence isredefined). For example, the last 20-bits from a previous payloadsequence and the first 44-bits from a current payload sequence can becollected. The method then proceeds to step 422.

At step 422, if the CRC of this new 64-bit sequence matches the embeddedCRC, then the payload has been correctly decoded and the method 400 isexited. If new 64-bit sequence does not match the embedded CRC, themethod 400 can return to step 420. The method 400 of the presentinvention can perform various iterations of step 420 in an attempt todetermine a payload sequence that can be correctly decoded.

Although the methods above are described with reference to an encoderand a decoder, the inventive aspects of the present invention are not solimited. The marker symbol selection, marker code selection, marker codeencoding and the marker code decoding of the present invention can beimplemented in stand alone devices not included in an encoder anddecoder. As such a stand alone marker generation/coding device inaccordance with one embodiment of the present invention can perform amethod including determining at least one marker symbol and acorresponding marker code such that when the digital content is codedusing the marker code, the marker symbol is not repeated by the codeddigital content, embedding the determined marker symbol in anidentifiable location in a payload of the digital content, and markercoding the payload of the digital content using the determined markercode to form a periodic sequence as described above. That is, when astand alone marker generation/coding device in accordance with oneembodiment of the present invention is applied, not all of the methodsteps of, for example, the method 300 of FIG. 3 are performed in thestand alone marker generation/coding device. Instead, the traditionalencoding steps will be performed in an associated encoder.

Similarly, a stand alone marker code decoding device in accordance withone embodiment of the present invention can perform a method includingreceiving digital content having an embedded, unique marker symbol in apayload of the digital content, the digital content having been encodedvia a marker code to form a periodic sequence, temporally synchronizingthe digital content for decoding by identifying the marker symbol in thepayload of the digital content, the marker symbol marking anidentifiable location in the payload for use in decoding the payload ofthe digital content, and decoding the payload of the digital contentusing at least a location of the identified marker symbol and the markercode as described above. That is, when a stand alone marker codedecoding device in accordance with one embodiment of the presentinvention is applied, not all of the method steps of, for example, themethod 400 of FIG. 4 are performed in the stand alone marker codedecoding device. Instead, the traditional decoding steps will beperformed in an associated decoder.

Having described various embodiments for a method, apparatus and systemfor temporal synchronization of digital content based on, for example, aunique marker symbol and corresponding marker code (which are intendedto be illustrative and not limiting), it is noted that modifications andvariations can be made by persons skilled in the art in light of theabove teachings. It is therefore to be understood that changes may bemade in the particular embodiments of the invention disclosed which arewithin the scope and spirit of the invention as outlined by the appendedclaims. While the forgoing is directed to various embodiments of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof.

1. A method for temporal synchronization of digital content, comprising:determining at least one marker symbol and a corresponding marker codesuch that when said digital content is coded using said marker code,said marker symbol is not repeated by said coded digital content;embedding said determined marker symbol in an identifiable location in apayload of said digital content; and coding the payload of said digitalcontent using said determined marker code to form a periodic sequence;wherein the payload of said digital content is temporally synchronizedfor decoding by identifying said marker symbol in the payload of saiddigital content, said marker symbol marking an identifiable location inthe payload for use in decoding said payload of said digital content. 2.The method of claim 1, further comprising error correction coding saiddigital content.
 3. The method of claim 1, wherein said marker symbol isembedded in said digital content at a regular interval.
 4. The method ofclaim 3, wherein said regular interval comprises a payload interval. 5.The method of claim 1, wherein marker code words of said marker code areselected such that marker code words that result in payload bitsresembling the marker symbol are not used for marker coding the payloadof the digital content.
 6. The method of claim 1, further comprisingembedding an additional synchronization signal into the payload of saiddigital content.
 7. The method of claim 1, further comprising encodingsaid coded digital content for transmission to a decoding device.
 8. Themethod of claim 1, further comprising appending a CRC code to thepayload of said digital content.
 9. A method for temporalsynchronization of digital content, comprising: receiving digitalcontent having an embedded, unique marker symbol in a payload of saiddigital content, said digital content having been coded via a markercode to form a periodic sequence, temporally synchronizing said digitalcontent for decoding by identifying said marker symbol in the payload ofsaid digital content, said marker symbol marking an identifiablelocation in the payload for use in decoding said payload of said digitalcontent; and decoding the payload of said digital content using at leasta location of said identified marker symbol and said marker code;wherein said received marker coded digital content further undergoesextraction and error correction decoding.
 10. The method of claim 9,wherein in response to a marker symbol in the payload of said digitalcontent not being identified, a maximum likelihood principle is appliedto the payload of said digital content to determine which payloadsequence is most likely the marker symbol embedded in the content. 11.The method of claim 9, further comprising examining a cyclic redundancycheck (CRC) code appended to the payload of said digital content todetermine if said digital content has been properly decoded.
 12. Themethod of claim 11, wherein if an examined CRC code does not match a CRCcode appended to the payload of said digital content during an encodingprocess, payload bits surrounding an identified marker symbol areregrouped in an attempt to locate and identify said appended CRC code insaid digital content.
 13. An apparatus for temporal synchronization ofdigital content for use in encoding said digital content, comprising: amarker generation/coding unit configured to: determine at least onemarker symbol and a corresponding marker code such that when saiddigital content is coded using said marker code, said marker symbol isnot repeated by said coded digital content; embed said determined markersymbol in an identifiable location in a payload of said digital content;and code the payload of said digital content using said determinedmarker code to form a periodic sequence.
 14. The apparatus of claim 13,wherein said apparatus comprises an encoder.
 15. The apparatus of claim13, wherein said marker symbol and corresponding marker code are used inwatermarking audio and/or video digital content
 16. The apparatus ofclaim 13, further comprising a transmitter for communicating said codeddigital content to a decoding device.
 17. A system for temporalsynchronization of digital content, comprising: a markergeneration/coding unit configured to: determine at least one markersymbol and a corresponding marker code such that when said digitalcontent Is coded using said marker code, said marker symbol is notrepeated by said coded digital content; embed said determined markersymbol in an identifiable location in a payload of said digital content;and code the payload of said digital content using said determinedmarker code to form a periodic sequence; and a marker decoding unitconfigured to: receive digital content having an embedded, unique markersymbol in a payload of said digital content, said digital content havingbeen coded via a marker code to form a periodic sequence, temporallysynchronize said digital content for decoding by identifying said markersymbol in the payload of said digital content, said marker symbolmarking an identifiable location in the payload for use in decoding saidpayload of said digital content; and decoding the payload of saiddigital content using at least a location of said identified markersymbol and said marker code.
 18. The system of claim 17, furthercomprising an output device for presenting said decoded digital content.